By:
Tim Wusz

Answers
to the question of compression ratio limits
for the various grades of Rockett
Brand Racing Gasoline
are compiled in this bulletin
to assist Rockett Brand Racing
Gasoline distributors in
making recommendations to their customers.
Many things besides compression ratio contribute
to the “octane requirement” (OR) of an engine,
so read on carefully.

The
following is a list of the most significant
items that contribute to OR. These must
be kept in mind when thinking about engine
OR.

1.
Compression Ratio...Higher requires more
octane

2.
Cylinder bore...Bigger bore requires more
octane

3.
Cast iron heads...Needs more octane then
aluminum heads

4.
Restrictor plates...Less restriction requires
more octane

5.
Lean mixtures...Need more octane

6.
Coolant temperature...Higher needs more
octane; 160 °
is
ideal

7.
Spark advance...More spark advance requires
more octane

8.
Intake air temperature...High temperature
needs more octane

9.
Humidity...dry air (low humidity) requires
more octane

10.
Barometric Pressure...Higher needs more
octane

11.
Altitude...Closer to sea level needs more
octane

The
above information is a guide as to which
way the engine octane demand will go as
these eleven key parameters are changed.
There are other things that impact engine
octane requirement, but those listed above
are the most significant.

Summary
of Product Applications

Rockett
Brand 100 Octane Unleaded Racing Gasoline

This
product has been used in endurance racing
in four inch bore engines with 14:1 compression
ratio and aluminum heads. With cast iron
heads, compression ratios should be limited
to 13:1.

Rockett
Brand 100 Unleaded Racing Gasoline

This
product is street legal in all states and
used in current performance cars. Historic
muscle cars from the 1950’s and 1960’s can
also benefit from this product. It can readily
satisfy the compression ratios found in
many engines from that era.

Rockett
Brand 111 Racing Gasoline

This
product has been used in Winston Cup Racing
Engines with compression ratios as high
as 16:1 without restrictor plates and as
high as 19.5:1 with restrictor plates. The
Winston Cup Series uses small block Chevrolet
and Ford engines with aluminum heads and
four inch bores.

Some
engines are temperamental to tune with ultra
high compression ratios. It is best stay
below 16:1 to be on the safe side. If the
engine to be used has a bore that is smaller
than four inches, and has aluminum heads,
it may be safe to bump the compression ratio
up, but tuning may still be difficult.

Rockett
Brand 114 Racing Gasoline

This
gasoline was designed for big block racing
engines with 16:1 compression ratio. It
is a particularly good gasoline for drag
racers with high compression ratio big blocks
that want the same quality every time they
buy gasoline.

Other
applications for this product include normally
aspirated big block boat engines, as well
as those equipped with superchargers or
turbochargers.

This
gasoline can also be used in small block
engines where the engine builder wants a
greater margin of safety over Rockett
Brand 111 Racing Gasoline.

Rockett
Brand 118 Racing Gasoline

This
is a very good gasoline for high RPM drag
racing engines. It was developed using an
NHRA ProStock 500 cubic inch engine with
the power curve optimized between 7,000
and 9,000 RPM.

Another
application for this product is very high
boost supercharged or turbo-charged big
block engines. It has plenty of octane and
power potential for these high output engines.

This
gasoline has been used with very good results
in nitrous oxide equipped racing engines.
The high octane quality of this product
provides safety from detonation when used
in these high output applications.

Rockett
Brand 118 Racing Gasoline
has also been used in high RPM motorcycle
engines with numerous wins in NHRA competition.
These Pro Stock Bike engines have 17.5:1
compression ratio and run at speeds up to
14,000 RPM.

Other

If
your engine builder has a gasoline octane
recommendation, it is wise to follow his
advice rather than venturing into the unknown.